Inspection of different kinds of cereals and other crops is today made all over the world to determine the quality of the cereals in commercial transactions and handling. The inspection aims at examining a selected representative sample from a large consignment and determining the presence of non-desirable grains and particles. The non-approved grains and particles are classified and the quantity of each class is determined. Owing to the distribution of the various grains, the sample and, thus, the consignment will be given a grading, which is a decisive factor in connection with payment and handling of the consignment.
It is desirable that the classification be made by means of some kind of automated process. The analyses performed on these samples are often based on the sample material being irradiated by some kind of light. The sample is then analyzed by means of, for example, spectroscopic measurements, measurements on fluorescent light or image analysis. An analysis instrument for such measurements may comprise a mechanism, which positions sample material in a suitable place for irradiation by one or more light sources, and one or more sensors that measure the light that has interacted with the sample material.
In order to establish a reliable result from the analysis, measurements should be performed on several different and separate objects. This could be achieved in three different ways. The first alternative is to advance a new measurement object in front of the sensor for each part of the measurement. The second alternative is to move the sensor to a new measurement object for each part of the measurement and the third alternative is to measure several objects in one recording.
Due to measuring difficulties and handling reasons, the first alternative is normally preferable. The sensor is normally connected to analysis equipment for analysis of measurement results, and to a power supply. This makes movement of the sensor according to the second alternative complicated and undesirable. If several objects are measured in one recording according to the third alternative, it is often difficult to record variations among the objects. Further, certain set-ups for the irradiation are impossible to achieve for this alternative.
The first alternative requires some kind of sample-feeding mechanism, where the measurement object is placed in a sample holder, which is then advanced to a correct measurement position for the analysis. In order to speed up the sample feeding, several sample holders are often used, so that the placement of the sample in the sample holder, the measurement of the sample and the removal of the sample from the sample holder could be performed simultaneously in different positions.
It is often important that the samples be irradiated in a specific way. It is desired that a fixed light source be arranged at the measurement position, but for some irradiation arrangements this could be difficult to achieve. For example, in certain types of analyses, each particle is irradiated from a side of the particle, i.e. using radiation having a large angle of incidence in relation to a measuring direction from the particle towards a sensor. Such an analysis is preferable when determining the existence of cracks in rice grains. Irradiation from a side of the particle could also be of interest, when shadows are to be removed in different types of image analysis.
For such irradiation arrangements, radiation sources could be arranged to follow the feeding of the particle samples in order to irradiate the samples properly. However, this implies that a radiation source has to be arranged in connection to each sample holder. These radiation sources could have varying characteristics, which will affect the measurements and deteriorate the reliability of the measurements. Further, power supply has to be provided to a moving radiation source, which makes the arrangement complicated.